Systems which convert between color video signals and grey scale video signals are known in the art, as are systems employing digitally encoded video information, such as disclosed, by way of example, in U.S. Pat. Nos. 4,233,601; 4,345,276; 4,437,093; 4,373,156; 4,232,311; 4,368,484; 4,481,509; 4,481,594; 4,425,581 and 4,270,125. However, none of these prior art systems known to applicants is readily capable of use in systems where it is desired to inexpensively transmit color video information great distances over single coaxial cables to RGB type of monitors such as normally employed with computer displays, such as an IBM PC. Moreover, no such systems are known to applicants which also readily permit received conventional black and white video information to be displayed on the same RGB monitor as received digitally encoded color video information. Furthermore, in this regard, applicants are not aware of any prior art color decoders or systems which employ a 16 level grey scale code, i.e. 16 levels of grey to encode the video signal into 16 possible R,G,B,I color combinations, to provide the four R,G,B,I color bits over a single coaxial cable with no loss of bandwidth in an efficient and cost effective manner. These disadvantages of the prior art are overcome by the present invention.